The hoatzin, extraterrestrial bird

This funny story emerges from the extensive analysis carried out by geneticists to reconstruct the evolutionary epic of birds: this mad conquest of the sky led by a handful of surviving dinosaurs.

This project called “10,000 Genomes” was launched in 2015. The goal: to sequence and classify the genetic sequence of a representative of the 34 known orders of birds, then of a representative of the 240 families, then one of the 2250 genera, and finally a representative of about 8000 different species. Enough to draw up a beautiful evolution tree!

In the coming days, the international team will submit its work for the 240 families to publication (the level of the orders has already been done). And, already, they notice it: there is an intruder, an unclassifiable, a different: the hoatzin. “An abominably recalcitrant species”, told us one of the researchers. The hoatzin, or “sassa” in Guyanese Creole, is a bird the size of a pheasant, which lazes in the foliage of the Amazonian mangroves. And his behavior, already, is bizarre.

Unique among birds, it ruminates like a cow: its chest has given way to a huge crop where leaves and buds are fermenting. Other quirks: the baby bird instinctively knows how to swim, even underwater; it has a pair of dinosaur-like claws on each wing that allow it to climb trees; and he can move on all fours, like a quadruped. But the most mysterious is its genome: it is the only bird that has no cousin species still alive. He is lost in the tree: he is the only representative of his order, cut just for him, for lack of anything better.

For morphological reasons, it had long been related to hens, then to cuckoos. For genetic reasons, it was then approached to the group of “land birds” (like the peacock), then to the order of shorebirds, small waders. But, even with the new sequencing, nothing to do: the vagueness remains.

Without a common ancestor with other birds, it is impossible to trace the origin of its branch. According to some, the mystery of the hoatzin may never even be solved. He may therefore forever remain the most mysterious of all birds. A true alien…

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